Members of the Crawford family, Emily, Alison, Chris and Sam, are having fun at home when they are suddenly assaulted. Later they are found murdered. Morgan thinks the father, Chris Crawford, murdered his family then himself because the murder weapon is found near him. JJ thinks differently as she shows a crime photo of another family, the Millers, who had been killed earlier. The motive and killings seem similar so the murder/suicide scenario is thrown out. At the crime scene, the team discovers the husband's wedding ring is missing and the dog of the family is gone but his collar is found, which helps the case because the doggie door is equipped with a special alarm system that is attached to the collar.
The investigation makes Eric Miller (the husband) the lead suspect in this case seeing the similar motive. This time Gideon asks Dr. Reid to interrogate Miller, a task he's afraid to do. Miller denies murdering his family despite his physical abuse record. Reid believes his story saying that Eric still kept his wedding ring in memory of his dead wife.
Upon investigating the background of the Crawfords, it's found they were heavily in debt and Alison Crawford was spending a lot more than she or the family had. At the crime scene, as Morgan and Gideon discuss who may have entered the house, Gideon is puzzled to why no one heard the Crawfords' scream for help. Morgan, Hotchner, Reid and Gideon now think someone close to the Crawfords killed them.
The team finds Alison's brother, Frank, and brings him in for questioning when he's found with the family dog. He tells them that he, Alison, and Chris had had an argument, but revealed there was a stranger with them.
The investigation takes a turn to the actual breaking in. However, with no leads, they are now able to confirm the family had been held hostage before they were killed.
Another family is taken hostage.
Morgan profiles the unsub's behavior. He or she is probably very compulsive and meticulous, and probably is some sort of office worker. Morgan sees that Chris Crawford worked for the IRS and that Reese Miller (the late wife of the other family) worked at GAO. Tracing the background of the Millers, Dr. Reid comes up with the idea to look at their medical histories. The name Dr. Rachel Howard pops up so the investigation seeks to question her. However, Dr. Howard says she met the Millers and Crawfords only once, which gave her a good alibi. She does, however, say that Karl Arnold took over her case with the Millers. Upon entering Arnold's office, they find Emily Crawford's drawings and other items. Gideon now thinks he has his man. They try to find Arnold by calling his wife, but she doesn't know where he is.
They finally find Karl Arnold, but JJ says they can't hold since they don't have any forensic evidence. Gideon and Morgan interrogate Arnold who does not confess but shows he knew both families and was stalking them. Arnold says he planned to take them both down seeing as how Eric Miller was a terrible father and Alison Crawford was a lying wife and mother. Arnold still shows his compulsive behavior as he says that the crime photos he's seeing are not arranged well. This gives the team the idea that there are more clues still at Karl Arnold's office.
Hotchner finds a secret compartment in the wall of Arnold's office that contains videos of the families and then he finds a small box. He opens the box and finds all the wedding rings from the murdered husbands as well as a few previously unaccounted rings. This discovery proves Arnold is guilty, but also proves that Eric Miller is innocent.